Vegetable · Brassicaceae
Kohlrabi
Brassica oleracea Gongylodes Group
Grow it fast and cool, pick it while it's small, and kohlrabi rewards you with a crisp, sweet bulb sitting right on the soil.
Full sun
Every 3–7 days
64–75°F · 18–24°C
45–60 days
Overview
Kohlrabi looks a bit unusual at first, a pale or purple globe resting on the soil with leaves sprouting straight out of the top, so don't be put off if it seems strange. It's part of the cabbage family, the very same species as broccoli, kale, and cabbage, only coaxed to swell its stem instead of its head or leaves. Raw, it tastes like a gentle cross between a mild turnip and a broccoli stem, crisp and just a touch sweet, and it's genuinely lovely fresh from the garden.
This is a cool-season crop that feels most at home in the mild days of spring and fall, and it's wonderfully forgiving to grow. It ripens fast, often in comfortably under two months, so plenty of gardeners fit two crops into a single year. The secret is simple: a bulb that grows quickly and gets picked young stays tender, while one that struggles through heat or waits too long turns tough. If yours does turn tough, that's an easy fix, just pick the next one sooner.
It's a kind plant for anyone short on time or space, and a reassuring first vegetable to try. The plants stay small, brush off a light frost, and ask for little more than steady water and decent soil. Get the timing roughly right and you'll be pulling crisp bulbs with hardly any fuss, feeling every bit the capable gardener.
Care
The short version: give kohlrabi full sun and cool weather with steady moisture, about an inch of water a week so the bulbs stay tender, plant it in rich, well-drained soil, and pick it young at 2 to 3 inches across.
Light
Give kohlrabi full sun, at least six hours a day, and it will grow along steadily and happily. It also takes partial shade in hot weather, which is actually a help in summer, since the cooler shade keeps the plants comfortable and slows them down before they bolt.
Water
Aim for even, consistent moisture, roughly an inch of water a week, and you'll have done the most important thing of all. Steady water is what grows tender, mild stems, while a plant that dries out and then bounces back tends to turn tough, woody, and bitter.
Soil
Plant into loamy, well-drained soil with a good helping of organic matter worked in, and it will feel right at home. A pH of 6.0 to 7.5 suits it nicely, and leaning toward the higher end gives you a little insurance against clubroot, the disease that troubles the cabbage family.
Temperature
Kohlrabi is happiest in cool air between 64°F and 75°F (18°C to 24°C), so you don't need to fuss much. It shrugs off a light frost, but heat is the thing to avoid, since warm spells can push it to bolt and leave the bulbs tough.
Humidity
Ordinary outdoor humidity is plenty, so there's no number you need to chase and nothing extra to set up. What truly counts is steady soil moisture, and that's what keeps the bulbs crisp for you.
Feeding
Work a balanced or low-phosphorus fertilizer into the bed at planting, ideally guided by a soil test if you can manage one. Then side-dress with a bit of nitrogen once the plants stand about 4 inches tall, which keeps them growing along nicely.
Pruning
Good news here, kohlrabi needs no pruning whatsoever. The only leaves you'll ever remove are lower ones that turn ragged from pests or disease, and those you simply pull off and toss out rather than leave on the plant.
Size & spacing
These are small, manageable plants, reaching just 6 to 12 inches (15 to 30 cm) tall and about as wide, so they won't overwhelm a bed. Space the standard varieties around 4 inches (10 cm) apart, giving each one room to swell its bulb without feeling crowded.
When to plant
Kohlrabi is a cool-weather crop that would rather skip the summer heat, and it makes timing easy on you. Sow it in early spring for a late-spring harvest, then sow again in July so the bulbs finish up in the gentle cool of fall. Either way, both crops are ready in well under two months.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: early spring, 4 to 6 weeks before transplanting outdoors
- Plant: mid-April to early May for spring crop, or July for fall crop
- Harvest: harvest when the swollen stem reaches 2 to 3 inches in diameter
Hardiness
USDA hardiness zones: 3–9
Temperature: down to -40°C
Troubleshooting
Most kohlrabi troubles come down to timing and a few cabbage-family pests it shares with its relatives, and none of them need to scare you off. Spot them early and they're simple to head off. Match what you're seeing below, then step in before the bulb or the leaves take any real harm.
Wilting, stalled plants with troubled roots
When a plant droops and stops growing for no clear reason, gently ease it up and check underground. You may find the tunnels of cabbage maggots or the swollen, club-shaped lumps of clubroot. A sick plant can't be saved, so pull and destroy it, then move your brassicas to fresh ground on a four-year cycle and keep the soil pH on the higher side to hold clubroot back.
Fix:
- Remove and destroy affected plants
- Practice a 4-year rotation away from brassicas
Bulbs that turned tough and a little bitter
If a bulb feels woody, don't worry, it almost always just grew too big and is telling you to pick the next one earlier. Slice it open and a stringy inside means it lingered too long or pushed through heat and dry spells. Aim to harvest around 2 to 3 inches (5 to 8 cm) across and keep the soil evenly damp, and your stems will come out crisp and sweet.
Fix:
- Harvest at 2 to 3 inches in diameter for best quality
- Keep soil evenly moist to maintain fast, uninterrupted growth
Chewed, ragged holes across the leaves
Green caterpillars are the friendly culprits here, usually imported cabbageworms, cabbage loopers, or diamondback moth larvae, and they are easy to deal with. Turn a leaf over and you'll spot them near little dark specks of frass. Just pick them off, dab on some Bt if you like, and tuck young plants under a floating row cover so the moths never get a chance to lay eggs.
Fix:
- Handpick caterpillars
- Apply Bacillus thuringiensis (Bt) where appropriate
- Use floating row covers
Tiny pinholes dotting the young leaves
Those little specks come from flea beetles, and they'll hop off the second you brush the plant. It looks worse than it is, so take heart, a healthy seedling shakes this off with ease. Slip a row cover over the bed at planting and keep the plants well fed, and they'll grow right past the nibbling.
Fix:
- Use floating row covers at planting
- Maintain vigorous growth so plants outgrow damage
Toxicity
You can breathe easy here, because kohlrabi is completely safe, a food crop with nothing toxic in it for people or animals. Both the bulb and the leaves are edible, so a nibble from a curious pet is nothing to worry about. The only thing to keep an eye on is quantity, since any brassica can bring on gas, and a very large feed isn't ideal for horses.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
You can relax around cats, since kohlrabi is safe for them. A curious lick or nibble of leaf or stem won't hurt, even if most cats aren't that interested in it.
Dogs None
Feel free to share kohlrabi with a dog, as plain raw or cooked pieces make a fine treat. The worst a generous helping might bring is a little gas, so there's nothing to fear.
Horses Mild
A small nibble won't trouble a horse, but a big feed of any brassica can unsettle the gut or, over time, nudge the thyroid. Just keep it as an occasional treat and all is well.
Rabbits Safe
Rabbits are happy to eat both the leaves and the bulb. Offer a little at a time so their tummy can ease into a new green, and they'll do just fine.
Livestock Safe
Cattle, goats, and sheep can graze kohlrabi with no worry. As with any brassica, work it into the diet slowly rather than all at once and they'll settle in comfortably.
Birds Safe
Backyard hens and other birds will peck contentedly at the leaves and stem. Nothing in the plant can harm them, so you can let them enjoy it.
People Safe
Kohlrabi is meant for the table, raw or cooked, and it's safe for people of every age. Both the crisp bulb and the leafy tops are good, wholesome food.
As a brassica, large quantities can cause gas or mild goitrogenic effects; horses should not be fed large amounts.
Varieties
Only a small handful of kohlrabi varieties show up in most seed catalogs, sorted mostly by color and size, so choosing is refreshingly simple. These are the ones worth getting to know.
Purple Vienna
You'll know this heirloom by its deep purple skin, which wraps around flesh that stays a pale greenish-white inside.
White Vienna
This is the familiar pale green kind that gardeners love for its crisp, gently mild flesh.
Kossak
A big storage type that kindly stays tender even when it grows well past the size of ordinary kohlrabi.
How to propagate
Kohlrabi is grown from seed and nothing else, and honestly it's about as gentle an introduction to seed-starting as you'll find.
SeedEasy
Sow indoors in early spring 4 to 6 weeks before transplanting, or direct sow mid-April to early May and again in July for fall · 7 to 14 days to germinate, with bulbs ready 45 to 60 days from sowing
Take heart, kohlrabi comes up from seed with almost no effort and forgives a beginner's mistakes. Start it indoors in early spring roughly 4 to 6 weeks ahead of transplanting, or drop seed right into the ground from mid-April through early May and again in July for a fall picking. Tuck each seed 1/4 to 1/2 inch (6 to 13 mm) deep and thin the standard plants to 4 inches (10 cm) apart. You'll see green in 7 to 14 days, and the bulbs will be ready to pull 45 to 60 days after sowing.
Myths
Kohlrabi is a root vegetable like a turnip.
Here's the happy surprise: the part you eat sits above the soil, not down in it. That round globe is a swollen stem that puffs out from the base of the plant instead of digging downward like a root. The old name German turnip throws people off, because kohlrabi is really a brassica, far closer kin to cabbage than to any true turnip.